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Abstract:

A fine denier poly(trimethylene arylate) spun drawn fiber is
characterized by high denier uniformity. A process for preparing uniform
fine denier yarns at spinning speeds of 4000 to 6000 m/min is further
disclosed. The poly(trimethylene arylate) fiber hereof comprises 0.1 to
3% by weight of polystyrene dispersed therewithin. Fabrics prepared
therefrom are also disclosed.

Claims:

1. A process comprising extruding a polymer melt comprising 0.1 to 3% by
weight, based on the total weight of polymer, of polystyrene dispersed in
poly(trimethylene arylate), through an orifice forming a continuous
filamentary extrudate, quenching the extrudate to solidify it into a
continuous filament, wrapping the continuous filament around a first
driven roll heated to a temperature in the range of 60 to 100.degree. C.
and rotating at a first rotational speed, followed by wrapping the
filament around a second driven roll heated to a temperature in the range
of 100 to 130.degree. C. and rotating at a second rotational speed
wherein the ratio of the first rotational speed to the second rotational
speed lies in the range of 1.75 to 3; and, thereby forming a spun drawn
filament having a denier of ≦3, a denier coefficient of variation
of ≦3%, and a birefringence of ≧0.055.

2. The process of claim 1 wherein the poly(trimethylene arylate) is
poly(trimethylene terephthalate).

3. The process of claim 1 wherein the polymer melt consists essentially
of 0.5 to 3% by weight of polystyrene dispersed in poly(trimethylene
arylate).

4. The process of claim 2 wherein the polymer melt consists essentially
0.5 to 3% by weight of polystyrene dispersed in poly(trimethylene
terephthalate).

5. The process of claim 2 wherein the polymer melt comprises 0.5 to 2% by
weight of polystyrene dispersed in poly(trimethylene terephthalate).

6. The process of claim 1 wherein the first driven roll is heated to a
temperature in the range of 70 to 100.degree. C.

7. The process of claim 1 further comprising wrapping the filament around
a third driven roll rotating at a third rotational speed, and wherein the
ratio of the third rotational speed to the second rotational speed is
<1.

8. The process of claim 1 further comprising accumulating the filament at
a rate of at least 4,000 m/min.

Description:

FIELD OF THE INVENTION

[0001] This invention relates to a process for spinning poly(trimethylene
arylate) fibers, the resultant fibers, and their use.

BACKGROUND

[0002] Poly(trimethylene arylate), particularly poly(trimethylene
terephthalate) (also referred to as 3GT, Triexta or PTT), has recently
received much attention as a fiber-forming polymer useful in textiles.
PTT fibers have excellent physical and chemical properties. Continuous
textured polyester yarns, prepared from partially oriented polyester
yarns (POY) or spun drawn yarns (SDY), mostly polyethylene terephthalate
(PET), are in wide-spread commercial use in many textile applications,
such as knit and woven fabrics, as well as non-woven fabrics, such as
spunbonded PET. The textile term "yarn" refers to a bundle of individual
fibers. For example, shirts and blouses are often made from yarns made up
of bundles of 30-40 filaments.

[0003] Polyester yarns, including both PET and PTT yarns, are prepared by
a so-called melt spinning process, and are said to be "melt spun." Melt
spinning is a process whereby the polymer is melted and extruded through
a hole in a so-called spinneret. In typical textile applications, the
spinneret is provided with a plurality of holes, often 30-40, each about
0.25 mm in diameter. Multiple filaments are thereby extruded from a
single spinneret. Those filaments are combined to form a bundle that is
called a yarn.

[0004] Polyester yarns can be used in any combinations with or without
other types of yarns. Thus, polyester yarns can make up an entire fabric,
or constitute the warp, weft or fill, in a woven fabric; or as one of two
or more yarns in a yarn blend, for instance, with cotton, wool, rayon,
acetate, other polyesters, spandex and/or combinations thereof.

[0005] Fujimoto et al., U.S. Pat. No. 6,284,370, discloses a process for
preparing 1-2 dpf PTT fibers wherein a first roll is heated to
30-80° C., a second roll is heated to 100-160° C., and the
draw ratio imposed between the first and second rolls was is in the range
of 1.3-4. In 13 examples and 11 counterexamples, Fujimoto never heated
the first roll to a temperature above 60° C. except in one
counterexample. In all the example, the first roll temperature was in the
range of 50-60° C.

[0006] Ding, U.S. Pat. No. 7,785,507, discloses a process for preparing
2-3 dpf PTT fibers wherein a first godet is heated to 85-160° C.,
a second godet is heated to 125-195° C., and the draw ratio
imposed between the first and second rolls was in the range of 1.1-2.
Ding teaches that a first godet temperature of 75° C. caused
excessive line breaks. Uster results were ca. 0.90-0.95%. In all the
examples, the temperature of the first godet was 90° C. or more.

[0007] Howell et al., U.S. Pat. No. 6,287,688, describes preparation of
textured PTT yarns that exhibit increased stretch, luxurious bulk and
improved hand, as compared to PET yarns. Howell et al. describes
preparing partially oriented PTT yarns at spinning speeds up to 2600 m/m.
By contrast, PET is routinely melt spun at several times that speed. For
reasons of cost, it is highly desirable to be able to spin PTT yarns at
speeds higher than 2600 m/min.

[0008] Chang et al., U.S. Pat. No. 6,923,925, discloses a composition
comprising PTT containing about 2% polystyrene (PS) that can be melt spun
into spun drawn yarns at speeds up to 5000 m/min. Chang et al. is
completely silent in regard to the denier uniformity (Denier CV) of the
yarns so produced, and silent as well regarding the temperatures of the
godet rolls employed for preparing the spun drawn yarn.

[0009] There is a need for a low denier spun-drawn filament yarn of PTT
that can be spun at commercially viable spinning speeds and that is of
sufficient denier uniformity to have practical utility in the preparation
of high quality fabrics and garments.

SUMMARY OF THE INVENTION

[0010] In a first aspect, the present invention provides a filament
comprising a composition comprising 0.1 to 3% by weight of polystyrene,
based on the total weight of the polymer in the composition, dispersed in
poly(trimethylene arylate) wherein the filament is characterized by a
denier per filament of ≦3, a denier coefficient of variation of
≦2.5% and a birefringence of at least 0.055.

[0011] In one embodiment, the poly(trimethylene arylate) is
poly(trimethylene terephthalate).

[0012] In another aspect, the present invention provides a process for
forming a novel spun drawn filament characterized by a denier per
filament of ≦3, and a denier coefficient of variation of
≦2.5, the process comprising extruding a polymer melt comprising
0.1 to 3% by weight, based on the total weight of polymer, of polystyrene
dispersed in poly(trimethylene arylate), through an orifice having a
cross-sectional shape, thereby forming a continuous filamentary
extrudate, quenching the extrudate to solidify it into a continuous
filament, wrapping the filament on a first driven roll heated to a
temperature in the range of 70 to 100° C. and rotating at a first
rotational speed, followed by wrapping the filament on a second driven
roll heated to a temperature in the range of 100 to 130° C. and
rotating at a second rotational speed; and, winding said filament onto a
take-up roll at a linear speed of at least 4,000 meters/minute (m/min);
wherein the ratio of the first rotational speed to the second rotational
speed lies in the range of 1.75 to 3; thereby forming a spun drawn
filament having a denier per filament of ≦3, and a denier
coefficient of variation of ≦2.5%.

[0013] In one embodiment, the poly(trimethylene arylate) is
poly(trimethylene terephthalate).

[0014] In another aspect, the present invention provides a fabric
comprising a filament comprising a composition comprising 0.1 to 3% by
weight of polystyrene, based on the total weight of the polymer in the
composition, dispersed in poly(trimethylene arylate) wherein the filament
is characterized by a denier per filament of ≦3, a denier
coefficient of variation of ≦2.5% and a birefringence of at least
0.055.

[0015] In one embodiment, the poly(trimethylene arylate) is
poly(trimethylene terephthalate).

BRIEF DESCRIPTION OF THE DRAWING

[0016] FIG. 1 is a schematic representation of one embodiment of melt
feeding a spinneret according to the invention.

[0017] FIG. 2 is a schematic representation of one embodiment of the fiber
spinning process according to the invention.

[0018] FIG. 3 depicts a loom suitable for fabricating a woven fabric of
the invention.

[0019]FIG. 4 is a schematic representation of the spinning machines
employed in the Examples.

[0020] FIG. 5 is a graph of the experimental results, showing the effect
of the temperature of the first godet on the denier coefficient of
variation, and contrasting the results obtained using Spinning Machine #2
with those obtained using Spinning Machine #1.

DETAILED DESCRIPTION OF THE INVENTION

[0021] In one aspect, the present invention is directed to a filament
comprising a composition comprising--0.1 to 3% by weight of
polystyrene, based on the total weight of the polymer in the composition,
dispersed in poly(trimethylene arylate) wherein the filament is
characterized by a denier per filament (dpf) of 3, a denier coefficient
of variation (denier CV) of 2.5% and a birefringence of at least 0.055.

[0022] In one embodiment, the poly(trimethylene arylate) is
poly(trimethylene terephthalate).

[0023] In one embodiment, the filament hereof is a continuous filament. In
an alternative embodiment, the filament hereof is a staple filament. In
one embodiment, a plurality of the filaments hereof are combined to form
a multifilament yarn. The multifilament yarn thus formed is suitable for
for texturing, and for end uses in those textile applications in which
fine denier yarns are desirable, such as shirts, blouses, lingerie,
hosiery and the like.

[0024] The multifilament yarn hereof is useful for forming knitted, woven,
and non-woven fabrics by methods known in the art.

[0025] In an alternative embodiment, the filament hereof is also suitable
for use in a wide variety of non-woven constructions. The filament hereof
can be arrayed in a random or quasi-random web to form a filamentary
non-woven fabric. In a further embodiment, the filamentary non-woven
fabric comprises a plurality of continuous filament strands hereof. In an
alternative further embodiment, the filamentary non-woven fabric
comprises a single continuous filament strand. In an alternative
embodiment, the filamentary non-woven fabric comprises a plurality of
staple filaments prepared from the filament hereof. A filamentary
non-woven fabric for the purposes of the present invention is a non-woven
fabric whereof the fundamental structural element is a single randomly or
quasi-randomly disposed filament segment rather than a multi-filament
yarn segment.

[0026] In another aspect, the present invention provides a process for
forming a novel spun drawn filament characterized by a denier per
filament of ≦3, and a denier coefficient of variation of
≦2.5%, the process comprising extruding a polymer melt comprising
0.1 to 3% by weight, based on the total weight of polymer, of polystyrene
dispersed in poly(trimethylene arylate), through an orifice having a
cross-sectional shape, thereby forming a continuous filamentary
extrudate, quenching the extrudate to solidify it into a continuous
filament, wrapping the filament on a first driven roll heated to a
temperature in the range of 70 to 100° C. and rotating at a first
rotational speed, followed by wrapping the filament on a second driven
roll heated to a temperature in the range of 100 to 130° C. and
rotating at a second rotational speed; and, winding said filament onto a
take-up roll at a linear speed of at least 4,000 meters/minute (m/min);
wherein the ratio of the first rotational speed to the second rotational
speed lies in the range of 1.75 to 3.

[0027] As demonstrated in the examples presented infra, the denier CV of
yarns of ≦3 dpf when spun at speeds of 4,000 m/min or more when
the first godet is set above 70° C. is conspicuously lower than
that of yarns of comparable composition spun at the same speeds when the
first godet is set at the commercially typical temperature of 60°
C.

[0028] The term "denier coefficient of variation" (denier CV) refers to
the coefficient of variation in denier determined by a Uster Yarn
Evenness tester available from Uster Technologies. The so called "Uster
Tester" measures denier variation along the length of a single continuous
strand of fiber or yarn. The denier CV is a standard statistical
parameter that represents the value obtained by dividing the standard
deviation of the denier by the mean denier, determined from the Uster
Tester.

[0029] In the present invention concentrations are stated in terms of
percentages by weight unless otherwise stated. In particular, it shall be
understood that the concentration of polystyrene blended with the
poly(trimethylene terephthalate) or other poly(trimethylene arylate)
hereof is expressed as the percent by weight of polystyrene relative to
the total weight of polymer in the composition.

[0030] When a range of numerical values is provided herein, it shall be
understood to encompass the end-points of the range unless specifically
stated otherwise. Numerical values are to be understood to have the
precision of the number of significant figures provided as described in
ASTM E29-08. For example, the number 3 shall be understood to encompass a
range from 2.5 to 3.4, whereas the number 3.0 shall be understood to
encompass a range from 2.95 to 3.04.

[0031] For the purposes of the present invention, the description shall be
directed at those embodiments in which the poly(trimethylene arylate) is
poly(trimethylene terephthalate) (PTT) unless otherwise explicitly
stated. Extension of the invention to other poly(trimethylene arylates)
shall be made with adjustments in concentration by weight appropriate to
differences in the molecular weight of the particular arylate monomer
units involved, assuming equal degrees of polymerization.

[0032] Both homopolymers and copolymers of both polystyrene and PTT are
suitable for use in the present invention. For the purposes of the
present invention, it shall be understood that the term "copolymer"
encompasses not only dipolymers, but terpolymers, tetrapolymers and so
forth. The term "copolymer" shall be understood to encompass any number
of monomers polymerized together. For practical purposes, the vast
majority of applications are limited to homopolymers, dipolymers, and
terpolymers.

[0033] In one embodiment, the filament comprises a composition comprising
97 to 99.9 wt % of PTT and 3 to 0.1 wt % polystyrene (PS). In another
embodiment, the filament comprises a composition comprising 70 to 99.5 wt
% of PTT, 3 to 0.5 wt % of PS, and, optionally, up to 29.5 wt % of other
polyesters. In another embodiment, the filament comprises a composition
comprising 98 to 99.5 wt % of PTT and 2 to 0.5 wt % PS.

[0034] In one embodiment, the filament consists essentially of a
composition consisting essentially of 97 to 99.9 wt % of PTT and 3 to 0.1
wt % polystyrene (PS). In another embodiment, the filament consists
essentially of a composition consisting essentially of 70 to 99.5 wt % of
PTT, 3 to 0.5 wt % of PS and, optionally, up to 29.5 wt % of other
polyesters. In another embodiment, the filament consists essentially of a
composition consisting essentially of 98 to 99.5 wt % of PTT and 2 to 0.5
wt % PS.

[0035] Suitable PTT polymer is formed by the condensation polymerization
of 1,3-propanediol and terephthalic acid or dimethylterephthalate. One or
more suitable comonomers for copolymerization therewith is selected from
the group consisting of linear, cyclic, and branched aliphatic
dicarboxylic acids or esters having 4-12 carbon atoms (for example
butanedioic acid, pentanedioic acid, hexanedioic acid, dodecanedioic
acid, and 1,4-cyclohexanedicarboxylic acid, and their corresponding
esters); aromatic dicarboxylic acids or esters other than terephthalic
acid or ester and having 8-12 carbon atoms (for example isophthalic acid
and 2,6-naphthalenedicarboxylic acid); linear, cyclic, and branched
aliphatic diols having 2-8 carbon atoms (other than 1,3-propanediol) for
example, ethanediol, 1,2-propanediol, 1,4-butanediol,
3-methyl-1,5-pentanediol, 2,2-dimethyl-1,3-propanediol,
2-methyl-1,3-propanediol, and 1,4-cyclohexanediol; and aliphatic and
aromatic ether glycols having 4-10 carbon atoms, for example,
hydroquinone bis(2-hydroxyethyl)ether, or a poly(ethylene ether)glycol
having a molecular weight below 460, including diethyleneether glycol.
The comonomer typically is present in the PTT copolymer at a level in the
range of 0.5-15 mole %, and can be present in amounts up to 30 mole %.

[0036] The PTT can contain minor amounts of other comonomers selected so
that they do not have a significant adverse affect on properties. Such
other comonomers include 5-sodium-sulfoisophthalate, for example, at a
level in the range of 0.2 to 5 mole %. Very small amounts of
trifunctional comonomers, for example trimellitic acid, can be
incorporated for viscosity control. The PTT can be blended with up to 30
mole percent of other polymers. Examples are polyesters prepared from
other diols, such as those recited supra.

[0037] In one embodiment, the PTT contains at least 85 mol-% of
trimethylene terephthalate repeat units. In a further embodiment, the PTT
contains at least 90 mol-% of trimethylene terephthalate repeat units. In
a still further embodiment the PTT contains at least 98 mol-% of of
trimethylene terephthalate repeat units. In a still further embodiment
the PTT contains 100 mol % of trimethylene terephthalate repeat units.

[0038] In one embodiment, suitable PTT is characterized by an intrinsic
viscosity (IV) in the range of 0.70 to 2.0 dl/g. In a further embodiment,
suitable PTT is characterized by an IV in the range of 0.80 to 1.5 dl/g.
In a still further embodiment, suitable PTT is characterized by an IV in
the range of 0.90 to 1.2 dl/g.

[0039] In one embodiment, suitable PTT is characterized by a number
average molecular weight (Mn) in the range of 10,000 to 40,000 Da.
In a further embodiment suitable PTT is characterized by Mn in the
range of 20,000 to 25,000 Da.

[0040] In one embodiment, a suitable polystyrene is selected from the
group consisting of polystyrene homopolymer, α-methyl-polystyrene,
and styrene-butadiene copolymers, and blends thereof. In one embodiment,
the polystyrene is a polystyrene homopolymer. In a further embodiment,
the polystyrene homopolymer is characterized by Mn in the range of
5,000 to 300,000 Da. In a still further embodiment, Mn of the
polystyrene homopolymer is in the range of 50,000 to 200,000 Da. In a
still further embodiment Mn of the polystyrene homopolymer is in the
range of 75,000 to 200,000 Da. In a still further embodiment, Mn of
the polystyrene homopolymer is in the range of 120,000 to 150,000 Da.
Useful polystyrenes can be isotactic, atactic, or syndiotactic. High
molecular weight atactic polystyrene homopolymer is preferred.

[0042] PTT and PS are melt blended and, then, extruded in the form of a
strand that is subsequently cut into pellets. Other forms of melt
blending and subsequent comminution, such as into flake, chips, or
powder, can also be performed. Under some circumstances it may be
convenient to prepare pellets comprising a first PTT/PS blend with a
concentration of PS greater than 15% followeb by remelting the pellets
and diluting the remelt with additional PTT to form a second melt blend
having a concentration of PS that is ≦3%, and to extrude the
second melt blend into the filament hereof.

[0043] The filament hereof comprises a composition comprising PTT and PS.
In some embodiments, these will be the only two materials in the blend
and they will total 100 weight %. However, in many instances the blend
will have other ingredients such as are commonly included in polyester
polymer compositions in commercial use. Such additives include but are
not limited to other polymers, plasticizers, UV absorbers, flame
retardants, dyestuffs, and so on. Thus the total of the poly(trimethylene
terephthalate) and polystyrene will not be 100 weight %. Other polymers
can include for example polyamides that impart acid dyeability to the
yarn blend. In those instances in which additional, non-polyester,
polymers are added, the ratios of polyester to PS weight percent
concentrations remain the same as for those compositions that do not
include the other polymers.

[0044] According to the present invention, the PS is in the form of
particles having an average size of less than 500 nanometers. In one
embodiment, the polystyrene is polystyrene homopolymer at a concentration
of ≦2%; and, the poly (trimethylene arylate) is PTT comprising at
least 98 mol % of trimethylene terephthalate monomer units.

[0045] The filament of the present invention is characterized by a dpf
≦3, a denier CV of ≦2.5%, and a birefringence of at least
0.055. Typical physical properties of the filament hereof include a
tenacity above 3 grams per denier, and an elongation to break of 30 to
70%. In one embodiment, the filament denier is ≦2.5. In another
embodiment, the birefringence is at least 0.060.

[0046] In another aspect, this invention is directed to a process for
preparing a single or multifilament yarn comprising (a) preparing a melt
blend consisting essentially of PTT and 0.1 to 3 weight % (wt %)
polystyrene (PS), (b) melt spinning the polymer melt blend so prepared to
form one or more filaments of PTT containing dispersed PS.

[0047] The filament of the present invention is conveniently prepared as a
spun drawn filament--that is, a filament that has been fully drawn in the
spinning process. By fully drawn is meant that the filament after
quenching has been elongated close to the ultimate elongation to break
thereof. Preferably, the spinning comprises extruding the polymer blend
hereof through the one or more holes of a spinneret at a spinning speed
of at least 4,000 m/m. The term "spinning speed" refers to the rate of
spun fiber accumulation, such as on a mechanical wind-up.

[0048] The high birefringence of ≧0.055 that is characteristic of
the filament of the invention is a direct result of the high draw applied
to the filament in the spun-draw process. High birefringence is a
principle way of distinguishing spun-drawn filaments from
partially-oriented spun yarn that is subsequently draw-textured.

[0049] FIG. 1 is a schematic representation of one embodiment of a melt
spinning machine suitable for use in the present invention. Referring to
FIG. 1, PTT is produced in a continuous melt polymerizer, 1, from which
it is conveyed in molten form via transfer line, 2, to a counter-rotating
twin-screw extruder, 3, the twin screw extruder being provided with a
mixing zone. Simultaneously, pellets comprising PS are fed via a
weight-loss feeder, 4, or other pellet feeder means, to a satellite
extruder, 5, wherein the pellet is melted and fed in molten form via
transfer line, 6, to twin-screw extruder, 3, either at or upstream from
the mixing zone of the twin-screw extruder, 3. In the twin-screw extruder
a PTT/PS melt blend is formed. The resulting melt blend is fed via
transfer line, 7, to a spin block comprising a spinneret, 8, from which
one or more continuous filaments, 9, are extruded.

[0050] FIG. 2 depicts one suitable arrangement for melt spinning according
to the invention. 34 filaments 22, (all 34 filaments are not shown) are
extruded through a hole spinneret 21. The filaments pass through a
cooling zone 23, are formed into a yarn bundle, and passed over a finish
applicator 24. The cooling zone comprises an air quench zone wherein air
is impinged upon the yarn bundle at room temperature and at 60% relative
humidity with a velocity of 40 feet/min. The air quench zone can be
designed for so-called cross-air-quench wherein the air flows across the
yarn bundle, or for so-called radial quench wherein the air source is in
the middle of the converging filaments and flows radially outward over
360°. Radial quench is a more uniform and effective quench method.
Following the finish applicator 24, the yarn is passed to a first driven
godet roll 25, also known as a feed roll, set at 60 to 100° C., in
one embodiment, 70 to 100° C., coupled with a separator roll. The
yarn is wrapped around the first godet roll and separator roll 6 to 8
times. From the first godet roll, the yarn is passed to a second driven
godet roll, also known as a draw roll, set at 110 to 130° C.,
coupled with a second separator roll. The yarn is wrapped around the
second godet roll and separator roll 6 to 8 times. Draw roll speed is
4000 to 6000 m/min while the ratio of draw roll speed to feed roll speed
is in the range of 1.75 to 3. From the draw rolls, the yarn is passed to
a third driven godet roll 27, coupled with a third separator roll,
operated at room temperature and at a speed 1-2% faster than the roll
speed of the second godet roll. The yarn is wrapped around the third pair
of rolls 6 to 10 times. From the third pair of rolls, the yarn is passed
though an interlace jet 28, and then to a wind-up 29, operated at a speed
to match the output of the third pair of rolls.

[0051] Referring to FIG. 2, according to the process hereof, a quenched
filament is wound at least once but preferably a plurality of times
around the first godet roll so that the first godet roll applies a
drawing force on the extruded filament, causing it to draw down before
quenching; down stream from the first godet roll, the filament is wrapped
at least once but preferably a plurality of times around a second godet
roll in such manner that the second godet applies a drawing force on that
portion of the filament lying between the first and second godet rolls.
In the embodiment depicted in FIG. 2, from the second godet roll, the
filament is directed to a third godet roll which serves as a let down
roll, running at a speed 1-2% higher than that of the second (draw) godet
roll. From the third godet, the filament is directed to a wind-up. The
rate at which the filament is wound on the wind-up is described as the
spinning speed. In typical installations, the wind-up is a tension
controlled wind-up.

[0052] According to the present invention, the first godet roll is heated
to a temperature in the range of 70-100° C. and the second godet
roll is heated to a temperature in the range of 100-130° C. The
first godet roll is driven at a first rotational speed; the second godet
roll is driven at a second rotational speed. According to the present
invention the ratio of the second rotational speed to the first
rotational speed (the draw ratio) falls within the range of 1.75 to 3.

[0053] In one embodiment, a plurality of filaments, each individually of
the invention, are extruded through a multi-hole spinneret. The filaments
so extruded are combined to form a yarn. Typically the yarn is held
together by the application of some agitation, twisting, or both, of the
extruded filaments, or thread line, causing the interlacing of the
filaments. The yarn so formed comprises a plurality of filaments, each
filament characterized by a dpf ≦3, a denier CV of ≦2.5%,
and a birefringence of at least 0.055. In one embodiment, the filament
denier is ≦2.5. In another embodiment, the birefringence is at
least 0.060. Typical yarns comprise 34, 48, 68, and 72 filaments,
although the number of filaments combined to make a yarn is not limited
in any way.

[0054] Yarns formed according to the present invention are not limited
only to be made up of a plurality of filaments according to the
invention, but can contain other filaments as well. For example, a yarn
formed according to the invention can contain other filaments of other
polyesters as well as polyamides, polyacrylates and other such filaments
as may be desired. The other filaments can also be staple fibers.

[0055] The yarn formed according to the invention, which can be formed by
the spun-draw process described supra, is suitable for use as a feed yarn
for false twist texturing as commonly practiced in order to provide
textile-like aesthetics to continuous polyester fibers. While there are
several types of texturing equipment, all well-known in the art, the
texturing process comprises a) providing a yarn package as formed
according to the spinning process described supra; (b)unwinding the yarn
from the package, (c) threading the yarn end through a friction twisting
element or false-twist spindle, d) causing the spindle to rotate, thereby
imparting twist in the yarn upstream of the rotating spindle and
untwisting the upstream twist downstream from the rotating spindle along
with the application of heat; and (e) winding the yarn onto a package.

[0056] The invention enables an increase in productivity in the spinning
of fine denier (≦3 dpf) spun--drawn PTT yarns. The filament and
yarn thereof of the invention have been prepared at spinning speeds that
are 30 to 70% higher than the maximum spinning speed achievable with neat
PTT. The resulting yarn is characterized by an elongation and tenacity
within 20% of the elongation and tenacity of a PTT multifilament yarn
that only differs from the yarn of the invention in that it does not
contain the PS (and that has necessarily been spun at about 3000 m/min).
Thus, the yarns consisting essentially of the filaments of the invention
are useful in a wide variety of textile applications with only minor
adjustments needed in the textile machinery being used. The resultant
yarns are useful in preparing inter alia textured yarns, fabrics and
carpets, under the same or similar conditions to those used for PTT yarns
not containing PS and prepared at 3000 m/min.

[0057] In the filament of the invention, the PTT is a continuous phase or
"matrix" and the PS is a discontinuous phase dispersed within the PTT
matrix. In one embodiment, the size of the PS particles dispersed in the
PTT matrix is ≦500 nm. In a further embodiment, the size of the PS
particles dispersed in the PTT matrix is ≦200 nm.

[0058] The beneficial features of the present invention include the
ability to spin a fine denier, high strength, tough, spun drawn PTT yarn
at spinning speeds of 4000 m/min or higher. These beneficial features
depend upon both the fine particle size of PS and the volume homogeneity
of the dispersion of PS in the PTT that in turn depend upon the
application of sufficiently high shear melt blending. There is no
threshold particle size at which the spinning performance and/or physical
properties of the spun yarn suddenly degrades. Rather, as the PS particle
size gets larger, performance gradually deteriorates. At particle sizes
in the range of 500 nm or larger, denier CV gets progressively larger.
Similarly, there is no particular threshold of homogeneity in regard to
particle distribution in the PTT matrix. The better the uniformity of
dispersion, the more uniform the resulting spun filament will be. One
particularly valuable benefit of the present invention is the production
of spun-drawn yarns characterized by denier CV of less than 2.5%. Low
denier CV is especially important in the preparation of fine denier yarns
for textile applications. Unless the process by which the PS is dispersed
in PTT is characterized by shear forces sufficient to ensure a particle
size less than 500 nm and a sufficiently high uniformity of dispersion,
it is highly unlikely that the denier CV will be ≦2.5%.

[0059] The amount of shear force applied to the melt depends upon the
rotational speed of the mixing elements, the viscosity of the melt, and
the residence time of the melt in the mixing zone. If the shear forces
are too low there is a tendency for the PS to not break up to begin with,
or to agglomerate rapidly into droplets greater than 500 nm in size.

[0060] The melt blending process can be performed both batch-wise and
continuously. So called high shear mixers such as are commonly employed
in the art of polymer compounding are suitable. Examples of suitable
commercially available high shear batch mixers include, but are not
limited to, Banbury mixers and Brabender mixers. Examples of continuous
high shear mixers include co-rotating twin-screw extruders and Farrel
Continuous Mixers Counter-rotating twin screw extruders are also
suitable. In general, suitable high shear mixers are those that are
capable of exerting on a polymer melt a minimum shear rate of 50/s, with
100/s preferred. After melt blending the resulting blend can be
pelletized for later feeding to a spinning machine, or the melt blend can
be fed directly into a spinning machine. Another useful method is to
combine polymer melts. An example of this method would be to provide a
PTT melt from a continuous polymerizer to the first stage of a twin screw
extruder, and feeding a PS melt from a satellite extruder into the mixing
zone of the twin screw extruder, thereby creating a melt blend. In
another method the unmelted polymers may be dry-mixed, as by tumbling,
before being fed to a twin screw extruder for melt blending.

[0061] Average particle size greater than 500 nm is not preferred from the
standpoint of good fiber spinning performance. Additionally, spinning of
uniform filaments, both along a single end, and end to end, depends
expressly upon the homogeneity of the volume distribution of the PS
particles. While in no way limiting the scope of the invention, it is
speculated that in the actual melt processing thereof, the PS particles
melt to form molten droplets that are dispersed within a molten PTT
matrix.

[0062] The temperature in the melt mixer should be above the melting
points of both the PTT and the PS but below the lowest decomposition
temperature of any of the ingredients. Specific temperatures will depend
upon the particular attributes of the polymers employed. In typical
practice, melt temperature is in the range of 200° C. to
270° C.

[0063] In one embodiment, the concentration of the PS in the PTT/PS blend
pellets is in the range of 0.5 to 1.5%.

[0064] As indicated in FIG. 1, and as is generally true for melt spinning
of polymer fibers, the polymer melt is fed to the spinneret via a
transfer line. The melt input to the transfer line from the extruder is
in turbulent. However, the spinneret feed must be laminar in order to
achieve uniform flow through the plurality of holes in the spinneret. It
is in the transfer line that the melt flow shifts from turbulent to
laminar.

[0065] Filament spinning can be accomplished using conventional apparatus
and procedures that are in widespread commercial use. As a practical
matter, it is found that for spinning fine denier filaments of 3 dpf or
lower, a PS concentration of >3% leads to a degradation in mechanical
properties of the fiber so produced. It is further found that at 5% PS,
fine denier filaments cannot be melt spun at all.

[0066] Prior to melt spinning, the polymer blend pellets are preferably
dried to a moisture level of <30 ppm to avoid hydrolytic degradation
during melt spinning. Any means for drying known in the art is
satisfactory. In one embodiment, a closed loop hot air dryer is employed.
Typically, the PTT/PS blend is dried at 130° C. and a dew point of
<-40° C. for 6 h. The thus dried PTT/PS polymer blend is melt
spun at 250-265° C. into fibers.

[0067] In a typical melt spinning process, one embodiment of which is
described in detail, infra, the dried polymer blend pellets are fed to an
extruder which melts the pellets and supplies the resulting melt to a
metering pump, which delivers a volumetrically controlled flow of polymer
into a heated spinning pack via a transfer line. The pump must provide a
pressure of 10-20 MPa to force the flow through the spinning pack, which
contains filtration media (eg, a sand bed and a filter screen) to remove
any particles larger than a few micrometers. The mass flow rate through
the spinneret is controlled by the metering pump. At the bottom of the
pack, the polymer exits into an air quench zone through a plurality of
small holes in a thick plate of metal (the spinneret). While the number
of holes and the dimensions thereof can vary greatly, typically a single
spinneret hole has a diameter in the range of 0.2-0.4 mm. Spinning is
advantageously accomplished at a spinneret temperature of 235 to
295° C., preferably 250 to 290° C.

[0068] A typical flow rate through a hole of that size tends to be in the
range of 1-5 g/min. Numerous cross-sectional shapes are employed for
spinneret holes, although circular cross-section is most common.
Typically a highly controlled rotating roll system through which the spun
filaments are wound controls the line speed. The diameter of the
filaments is determined by the flow rate and the take-up speed; and not
by the spinneret hole size.

[0069] The properties of the thus produced filaments are determined by the
threadline dynamics, particularly in the region between the exit from the
spinneret and the solidification point of the filaments, which is known
as the quench zone. The specific design of the quench zone, air flow rate
across the emerging still motile filaments has very large effects on the
quenched filament properties. Both cross-flow quench and radial quench
are in common use. After quenching or solidification, the filaments
travel at the take-up speed, that is typically 100-200 times faster than
the exit speed from the spinneret hole. Thus, considerable acceleration
(and stretching) of the threadline occurs after emergence from the
spinneret hole. The amount of orientation that is frozen into the spun
filament is directly related to the stress level in the filament at the
solidification point.

[0070] The melt spun filament thereby produced is collected in a manner
consistent with the desired end-use. For example, for filament intended
to be converted into staple fiber, a plurality of continuous filaments
can be combined into a tow that is accumulated in a so-called piddling
can. Filament intended for use in continuous form, such as in texturing,
is typically wound on a yarn package mounted on a tension-controlled
wind-up. According to the invention, the rate of accumulation is at least
4,000 m/min.

[0071] Texturing imparts crimp by twisting, heat setting, and untwisting
by the process commonly known as false twist texturing. These
multifilament yarns (also known as "bundles") comprise the same number of
filaments as the spun drawn yarns from which they are made. Thus, they
preferably comprise at least 10 and even more preferably at least 25
filaments, and typically can contain up to 150 or more, preferably up to
100, more preferably up to 80 filaments. The yarns typically have a total
denier of at least 1, more preferably at least 20, preferably t least 50,
more preferably up to 250, and up to 1,500. Filaments are preferably at
least 0.1 dpf, more preferably at least 0.5 dpf, more preferably at least
0.8 dpf, and most preferably up to 3 dpf.

[0072] PTT staple fibers can be prepared by melt spinning the PTT/PS-blend
at a temperature of 245 to 285° C. into filaments, quenching the
filaments, drawing the quenched filaments, crimping the drawn filaments,
and cutting the filaments into staple fibers, preferably having a length
of 0.2 to 6 inches (0.5 to 15 cm). One preferred process comprises: (a)
providing a polymer blend comprising PTT and 0.1 to 3% PS, (b) melt
spinning the melted blend at a temperature of 245 to 285° C. into
filaments, (c) quenching the filaments, (d) drawing the quenched
filaments, (e) crimping the drawn filaments using a mechanical crimper at
a crimp level of 8 to 30 crimps per inch (3 to 12 crimps/cm), (f)
relaxing the crimped filaments at a temperature of 50 to 120° c.,
and (g) cutting the relaxed filaments into staple fibers, preferably
having a length of 0.2 to 6 inches (0.5 to 15 cm). In one preferred
embodiment of this process, the drawn filaments are annealed at 85 to
115° C. before crimping. Preferably, annealing is carried out
under tension using heated rollers. In another preferred embodiment, the
drawn filaments are not annealed before crimping. Staple fibers are
useful in preparing textile yarns and textile or nonwoven fabrics, and
can also be used for fiberfill applications and making carpets.

[0073] While the invention is primarily described with respect to
multifilament yarns, it should be understood that the preferences
described herein are applicable to monofilaments.

[0074] The filaments can be round or have other shapes, such as octalobal,
delta, sunburst (also known as sol), scalloped oval, trilobal,
tetra-channel (also known as quatra-channel), scalloped ribbon, ribbon,
starburst, etc. They can be solid, hollow or multi-hollow.

[0075] In another aspect, the invention provides a fabric comprising a
filament comprising a composition comprising 0.1 to 3% by weight of
polystyrene, based on the total weight of the polymer in the composition,
dispersed in poly(trimethylene arylate) wherein the filament is
characterized by a denier per filament of ≦3, a denier coefficient
of variation of ≦2.5% and a birefringence of at least 0.055. In
one embodiment, the poly(trimethylene arylate) is poly(trimethylene
terephthalate).

[0076] In one embodiment the filaments are bundled into yarns, and the
fabric is a woven fabric. In an alternative embodiment, the filaments are
bundled into at least one yarn, and the fabric is a knit fabric. In still
another embodiment, the fabric is a nonwoven fabric; in a further
embodiment the fabric is a spunbonded fabric.

[0077] In one definition, a nonwoven fabric is a fabric that is neither
woven nor knit. Woven and knit structures are characterized by a regular
pattern of interlocking yarns produced either by interlacing (wovens) or
looping (knits). In both cases, yarns follow a regular pattern that takes
them from one side of the fabric to the other and back, over and over
again. The integrity of a woven or knitted fabric is created by the
structure of the fabric itself.

[0078] In nonwovens, most commonly filaments are laid down in a random
pattern and bonded to one another by chemical or thermal means rather
than mechanical means. One commercially available example of a nonwoven
produced by such means is Sontara® Spun-Bonded Polyester available
from the DuPont Company. In some cases nonwovens can be produced by
laying down layers of fibers in a complex three dimensional topological
array that does not involve interlacing or looping and in which the
fibers do not alternate from one side to the other, as described in
Popper et al., U.S. Pat. No. 6,579,815.

[0079] Woven fabrics are made with a plurality of yarns interlaced at
right angles to each other. The yarns parallel to the length of the
fabric are called the "warp" and the yarns orthogonal to that direction
are called the "filling" or "weft." Each warp yarn is called an "end." As
can be seen in any fabric or clothing store, tremendous variations in
aesthetics can be achieved by variations in the specific ways the yarns
are interlaced, the denier of the yarns, the aesthetics, both tactile and
visual, of the yarns themselves, the yarn density, and the ratio of warp
to filling yarns. As a general rule, the structure of a woven fabric
imparts a certain degree of rigidity to the fabric; a woven fabric does
not in general stretch as much as a knitted fabric.

[0080] In the woven fabrics of the invention, at least a portion of the
warp comprises yarns comprising a filament comprising a composition
comprising 0.1 to 3% by weight of polystyrene, based on the total weight
of the polymer in the composition, dispersed in poly(trimethylene
arylate) wherein the filament is characterized by a denier per filament
of ≦3, a denier coefficient of variation of ≦2.5% and a
birefringence of at least 0.055. In one embodiment, the poly(trimethylene
arylate) is poly(trimethylene terephthalate).

[0081] In one embodiment, both the warp and fill comprise yarns comprising
the filament hereof. In one embodiment, the warp comprises at least 40%
by number of yarns comprising the filament hereof and at least 40% by
number of cotton yarns. In one embodiment the warp comprises at least 80%
by number of yarns comprising the filament hereof, and the fill comprises
at least 80% cotton yarn. As a general rule, there are greater physical
demands place upon warp yarns than fill yarns.

[0082] Woven fabrics are fabricated on looms, as they have been for
thousands of years. While the loom has undergone tremendous changes, the
basic principles of operation remain the same. FIG. 3a is a schematic
depiction of an embodiment of a loom, shown in side view. A warp beam,
31, made up of a plurality, often hundreds, of parallel ends, 32, is
positioned as the loom feed. Warp beam, 31, is shown in front view in
FIG. 3b. Shown in FIG. 3a is a two harness loom. Each harness, 34a, and
34b, is a frame that holds a plurality, often hundreds, of so called
"heddles." Referring to FIG. 3c, showing a front, blowup view of a
harness, 34, each heddle, 311, is a vertical wire having a hole, 312, in
it. The harnesses are disposed to move up or down, one moving up while
the other moves down. A portion of the ends, 33a, are threaded through
the holes, 312, in the heddles, 311, of upper harness, 34a, while another
portion of the ends, 33b, are threaded through the holes in the heddles
of lower harness, 34b, thereby opening up a gap between the ends 33a and
33b. In the type of loom shown, a shuttlecock, 36, is impelled by means
not shown--typically wooden paddles--to move or shuttle from side to side
as the harnesses move up and down. The shuttlecock carries a bobbin of
filler yarn, 37, that unwinds as the shuttlecock moves through the gap in
the warp ends. A socalled "reed" or "batten," 35, is a frame that holds a
series of vertical wires between which the ends pass freely. FIG. 3d
shows the reed, 35, in front view depicting the vertical wires, 313, and
the spaces between, 314, through which the warp yarns pass. The thickness
of the vertical wires, 314, determines the spacing of and therefore
density of warp yarns in the crossfabric direction. The reed serves to
push the newly inserted filler yarn to the right in the diagram into
place in the forming fabric, 38. The fabric is wound onto the fabric
beam, 310. The rolls, 39, are guide rolls.

[0083] The winding of a warp beam is a precision operation in which
typically the same number of yarn packages or spools as the desired
number of ends are mounted on a so-called creel, and each end is fed onto
the warp beam through a series of precision guides and tensioners, and
then the entire warp beam is wound at once.

[0085] Knitting is the process by which a fabric is prepared by the
interlooping of one or more yarns. Knits tend to have more stretch and
resilience than wovens. Knits tend to be less durable than wovens. As in
the case of wovens, there are many knit patterns, and styles of knitting.
According to the present invention, in one embodiment the fabric hereof
is a knit fabric comprising yarns comprising a filament comprising a
composition comprising 0.1 to 3% by weight of polystyrene, based on the
total weight of the polymer in the composition, dispersed in
poly(trimethylene arylate) wherein the filament is characterized by a
denier per filament of ≦3, a denier coefficient of variation of
≦2.5% and a birefringence of at least 0.055. In one embodiment,
the poly(trimethylene arylate) is poly(trimethylene terephthalate).

[0086] Further contemplated in the present invention are garments sewn
from fabrics of the invention. The garments hereof comprise a fabric
comprising yarns comprising a filament comprising a composition
comprising 0.1 to 3% by weight of polystyrene, based on the total weight
of the polymer in the composition, dispersed in poly(trimethylene
arylate) wherein the filament is characterized by a denier per filament
of ≦3, a denier coefficient of variation of ≦2.5% and a
birefringence of at least 0.055. In one embodiment, the poly(trimethylene
arylate) is poly(trimethylene terephthalate).

[0087] The fabrication of garments from fabrics is extremely well-known
art. The preparation of a garment from a fabric includes preparing a
pattern, usually from paper, or in computerized form for automated
processes, measuring the required fabric pieces, cutting the fabric to
prepare the needed pieces, and then sewing the pieces together according
to the pattern. A garment may be made exclusively one or more styles of
the fabric of the invention. Alternatively, a garment may be prepared by
combining one or more styles of the fabric of the invention with other
fabrics.

[0088] The invention is further described in the following specific
embodiments, but is not limited thereto.

EXAMPLES

Test Methods

Intrinsic Viscosity

[0089] The intrinsic viscosity (IV) of the PTT was determined using a
Viscotek Forced Flow Viscometer Y900 (Viscotek Corporation, Houston,
Tex.) Following the procedures of ASTM D-5225-92, a 0.4 g/dl solution of
PTT was formed in a 50/50 weight % solvent mixture of trifluoroacetic
acid and methylene chloride at 19° C. and the viscosity
determined. These measured IV values were correlated to IV values
measured manually in 60/40 weight % phenol/1,1,2,2-tetrachloroethane
following ASTM D 4603-96.

Number Average Molecular Weight

[0090] The number average molecular weight of polystyrene was determined
following ASTM D 5296-97. The same method was used for poly(trimethylene
terephthalate) except that the calibration standard was a poly(ethylene
terephthalate) with an Mw of 44,000 and hexafluoroisopropanol
solvent.

Tenacity And Elongation At Break

[0091] The physical properties of the filaments and yarns were measured
using an Instron Corp. tensile tester, model no. 1122. More specifically,
elongation to break, Eb, and tenacity were measured according to
ASTM D-2256.

Spinning Campaigns and Spinning Machine affect on Results

[0092] Fiber spinning was performed in four separate campaigns. As
described in greater detail infra, Campaigns #1, 3, and 4 were executed
on Spinning Machine #2, while Campaign #2 was executed on Spinning
Machine #1.

[0093] The results obtained from Spinning Machine #1 were scattered, as
shown in Table 4 and FIG. 5, and are not considered definitive. In
particular, the denier coefficient of variation was higher than the limit
as specified in the invention, and did not appear to vary systematically
with the temperature of the first godet

[0094] FIG. 5 is a graph showing the denier CV versus first godet
temperature wherein all of the data obtained from Campaigns 1, 3, and 4
are combined together and plotted with a diamond shape, and the data from
Campaign #2 is graphed using a triangle shape. As shown in Tables 3-6,
infra, not all data points obtained in the three campaigns wherein
Spinning Machine #2 was employed were obtained using the same set of
spinning conditions. Nevertheless, as seen in FIG. 5, the data from
Spinning Machine #2, shown as diamond shapes, showed a clear trend, where
first godet temperature in the range of ca. 75 to 85° C.
corresponded to a minimum in denier CV. A similar trend was not observed
in the data of Campaign #2.

[0095] Denier coefficient of variation is a measurement of short distance
denier variability, which is in turn, an indicator of the stability of
the melt spinning process. The melt spinning process can be unstable
because the spinning composition causes an instability. It can also be
unstable because the machine is unstable. It is clear from FIG. 5 that in
this case the high denier CV produced in Campaign #2 was an artifact of
the machine performance and design.

[0096] Spinning Machine #1 was a laboratory-built spinning machine
provided with only the most basic equipment to effect melt spinning.
Spinning Machine #1 was employed normally only to obtain the most basic
information about whether or not experimental compositions were capable
of being melt-spun into fiber. It was employed in Campaign #2 herein
because of a scheduling mix-up--Spinning Machine #2 was not available on
the day scheduled for Campaign #2. Spinning Machine #2 was a pilot plant
spinning line. Conditions thereon were fully scalable to full-size
commercial scale spinning lines. This was the spinning line of choice for
demonstrating the differences in results that are characteristic of the
invention.

[0097]FIG. 4 schematically depicts Spinning Machine #2. A silo drier, 41,
gravity fed a single screw extruder, 42, with dried resin blend pellets.
The output of the single screw extruder, 42, was fed directly, under
pressure, to the input of a gear pump, 43, provided with an overflow
port, 44. The output of the gear pump was supplied via a short (inches
long) transfer line, 45, to a six end spin pack, 46. of which four ends
were used. Each of four threadlines, 47 (one shown), was extruded from a
36 hole spinneret, (not shown) whereof each hole was characterized by a
round cross-section of 0.27 mm diameter and 0.50 mm in length. Each
threadline, 47, passed through a cross-flow quench air zone approximately
1.75 m in length, 48, with ambient air flowing across the threadline from
one side to another in campaign 1 and a radial quench air zone
approximately 1.75 m in length, 48, with ambient air flowing radially
around the threadline to produce even more uniform filaments in campaigns
3 and 4. Each thus quenched threadline was contacted to a finish roll,
49, and then wrapped 6-8 times around a first heated godet (feed roll),
410, and a corresponding first separator roll, 411, to keep the
threadlines apart. The threadline was then directed to a second heated
godet (draw roll), 412, and a second corresponding second separator roll,
413, through an interlace jet (not shown) and thence to a windup, 414.
Also not shown, each Godet was partially enclosed by a hot chest to
maintain temperature. The extruder was provided with 3 heating zones, and
a head zone at the output.

[0098] Spinning Machine #1 and Spinning Machine #2 were substantially the
same in regard to the layout described in FIG. 4. Once difference was
that the quench air chimney in Spinning Machine #1 was much narrower than
its counterpart on Spinning Machine #2.

[0099] In all the Examples and Comparative Examples, the average results
for four threadlines spun simultaneously under each set of conditions are
reported. The spinning machines were allowed to reach steady state after
a change in set-point conditions by running for ca. 45 minutes before a
test sample was prepared. When the composition of the polymer was
changed, the spinning machine was purged with PTT not containing PS. When
the spinneret was changed, the machine was purged in between spinning
experiments.

Preparation Of Polymer Blends

[0100] Samples of PS in PTT (0.8 and 0.55 wt %) were made by co-feeding
dried PTT and PS to a 30 mm T/S extruder. Sorona®Semi-Dull PTT resin
pellets (1.02 IV available from the DuPont Company, Wilmington, Del.)
polytrimethylene terephthalate was combined with polystyrene (168 M KG 2
available from BASF) pellets in the amounts shown in Table 1. The PTT was
dried in a vacuum oven with a nitrogen purge at 120° C. for 14
hours prior to use. The two polymers were individually weight-loss fed to
the fourth barrel section of a Werner & Pfleiderer ZSK-30
counter-rotating twin screw extruder. The feed rates employed are shown
in Table 1 in pounds per hour (pph). The extruder had a 30 mm diameter
barrel constructed with 13 barrel sections provided in alternating
arrangement with two kneading zones and three conveying sections, the
extruder having an L/D ratio of 32. Each barrel section was independently
heated. Sections 1-4 were set at 25° C., Sections 5-13 were set at
210° C., the 3/16'' strand die was also set at 210° C. A
vacuum was applied to barrel segment 8. Table 1 also shows the
composition of the feed, the rate of output, and the melt temperature.
The extrudate was quenched in water immediately upon exiting the die and
was then pelletized using standard pelletizing equipment into 1/8''
pellets.

[0102] The melt compounded pellets of the PTT/PS blend so prepared were
dried in a drying silo overnight at 140° C. to lower the moisture
content to <50 ppm. The dried melt blends were gravity fed to the
single screw extruder described supra, in FIG. 4, of Spinning Machine #2.
Extruder set points, in ° C., in zones 1-3 were respectively
230/255/263. The extruder output was melt-fed to the spin pack through a
gear pump. The spin pack was provided with six spinning positions of
which four were provided with spinnerets each spinneret having 36 holes,
each hole being 0.27 mm in diameter and 0.5 mm in length, and of circular
cross-section. Each yarn so produced was a 75 denier 36 filament yarn.
The settings of the first godet roll are shown in Table 3. Note that the
second godet roll was maintained at 110° C. and 4500 rpm. The
quench air was a cross-flow quench with an air velocity of 0.35 cm/s.

[0103] The protocol that was followed was as follows: The second godet
roll (draw roll) was set at 4500 m/min and 110° C., and was not
changed in the course of the experiments. Experiments were then conducted
with the first godet roll (feed roll) set at 60° C. and the speed
was varied in order to identify a draw ratio that resulted in the highest
tenacity when elongation to break was adjusted to be in the range of
55-65%. For Polymer Blend #2 (0.055% PS) a draw ratio of 2.09 was found
to result in the highest tenacity when elongation to break was within the
desired range (i.e., the feed roll was set at 2150 m/min). Spinning was
then continued at additional feed roll temperatures of 85 and 110°
C. The same procedure was followed for Polymer Blend #1 (0.8% PS); a draw
ratio of 2.37 was found to result in the highest tenacity when elongation
to break was within the desired range (i.e., feed roll speed=1900 m/min).

[0105] A new melt blend of 0.80% by weight in PTT identical to that of
Blend #1 supra. The melt compounded pellets of the PTT/PS blend so
prepared were dried in a drying silo overnight at 140° C. to lower
the moisture content to <50 ppm. The dried melt blend pellets were
gravity fed to the single screw extruder described supra, in FIG. 4, of
Spinning Machine #1. Extruder set points, in ° C., in zones 1-3
were respectively 230/255/263. The extruder output was melt-fed to the
spin pack through a gear pump. The spin pack was provided with six
spinning positions of which four were provided with spinnerets each
spinneret having 36 holes, each hole being 0.27 mm in diameter and 0.5 mm
in length, and of circular cross-section. Each yarn so produced was a 75
denier 36 filament yarn. The settings of the first godet roll are shown
in Table 4. Note that the second godet roll was maintained at 110°
C. and 4500 rpm. The quench air was a cross-flow quench with an air
velocity of 0.35 cm/s.

[0106] The protocol that was followed was as follows: The second godet
roll (draw roll) was set at 4500 m/min and 110° C., and was not
changed in the course of the experiments. Experiments were then conducted
with the first godet roll (feed roll) set at 60° C. and the speed
was varied in order to identify a draw ratio that resulted in the highest
tenacity when elongation to break was adjusted to be in the range of
55-65%. The followed for Polymer Blend #1 (0.8% PS) was: a draw ratio of
2.37 was found to result in the highest tenacity when elongation to break
was within the desired range (i.e., first godet roll speed=1900 m/min).

[0107] Examples 5 and 6 were performed with spinneret orifices 0.27 mm in
diameter. Examples 7 and 8 were performed with spinneret orifices 0.32 mm
in diameter. Other spinning conditions are shown in Table 2 and Table 4.
Results are shown in Table 4.

[0108] The same batch of PS/PTT containing 0.80% by weight PS as employed
in Campaign #2 was employed.

[0109] Melt spinning was effected using the same spinning machine
procedures and settings as described for Campaign #1, supra, except that
in these examples a 75 denier/36 filament yarn was spun and the quench
was a radial quench. Spinning conditions are shown in Table 3 and Table
5. Again the extruder heating zones were set respectively to
230/255/263° C. Spinneret diameter was 0.27 mm. Flow rates were
controlled to 37.5 g/min. Results are shown in Table 5.

[0110] A third blend of 0.8% PS in PTT was made in a manner identical to
that of Blend #2, described supra.

[0111] Melt spinning was effected using the same spinning machine
procedures and settings as described for Campaign #3, supra, except that
in these examples a 75 denier/72 filament yarn was spun. Spinning
conditions are shown in Table 3 and Table 6. Again the extruder heating
zones were set respectively to 230/255/263° C. Spinneret diameter
was 0.27 mm. Flow rates were controlled to 37.5 g/min except where noted
in Ex 12 and Ex 13. Results are shown in Table 6.